As is well known, the products of combustion delivered to the 1st stage turbine are at the highest temperature that the engine sees. It is equally well-known that engine efficiency is directly related to this temperature and the higher the temperature the more efficient the engine. Obviously, technology dictates that this temperature be as high as the thermal integrity of the component parts will allow and with the advent of higher temperature resistance alloys these temperatures have been exceedingly high.
In certain engine models, because of the increase in the temperature the component parts in proximity to the turbine/combustor have been experiencing high local metal temperatures resulting in burning, buckling and cracking problems. The problem area in which this invention is directed is best seen in FIG. 1a showing the heretofore assembly. The FIG. 1a is a partial showing of an annular combustor for a twin spool axial flow turbine power plant of the type exemplified by the engine models JT9D, PW2037 and PW4000 manufactured by Pratt & Whitney of United Technologies Corporation, the assignee of this patent application.
As noted in FIG. 1A (prior art), the inner and outer louver liners 10 and 12 are suitably attached to the vane supports 14 and 16 which are ultimately tied to the inner case 18 and outer case 20 all in a well-known manner. As is obvious from this construction, the inner and outer louver liners are constrained at the discharged end in a toroidally shaped body and define a passageway for leading the engine's working fluid into the space between the vanes 22 (one being shown) to impinge on the turbine blades 24. In this construction and as is apparent from FIG. 1B which is a projected view of FIG. 1A and as shown by the arrows, the cooling air which is introduced from the annular cavity 26 which is fed by the engine's compressor (not shown) is directed toward the critical parts of the vane assembly to assure that these parts withstand the hostile environment.
However, the problem in this design, as shown by the arrows in FIGS. 1A and 1B, the hot spots identified by reference letter A, is caused by high temperature, high velocity of the engines working fluid being displaced by the vane's leading edge 30, and consequently, migrating to the vane platforms 32 and 34 and the burner trailing edge 36 (in proximity to the location of the arrows B).